1. Field of the Invention
The present invention relates to an inkjet head operable to eject an ink onto a recording medium, and a process of manufacturing the inkjet head.
2. Discussion of Related Art
Conventionally, there is known, as an inkjet head operable to eject an ink, an inkjet head including an ink channel unit which defines a network of ink channels and which includes a laminated structure body provided by a plurality of plates superposed on each other. US 2004/0183867 A1 (corresponding to JP-2004-276562A) discloses such an inkjet head including an ink channel unit defining a manifold chamber, a plurality of individual ink channels and a plurality of nozzles which are held in communication with the manifold chamber via the respective individual ink channels. This ink channel unit consists of a laminated structure body provided by a plurality of metal plates that are superposed on each other. The superposed metal plates may be fixed to each other by suitable means such as adhesive and diffusion welding.
Where the plurality of metal plates providing the laminated structure body are fixed to each other by diffusion welding, the metal plates are heated at a high temperature (about 1000° C.) under a vacuum condition while being gripped by a pair of jig members having respective flat contact surfaces such that the flat contact surfaces are respectively held in contact with opposite end ones of the superposed metal plates, so that the metal plates are fixed at their mutually contacted surfaces to each other, by causing diffusion of metallic atoms between the mutually contacted surfaces. This diffusion welding enables the plurality of metal plates to be fixed to each other in a single step, thereby making it possible to simplify the manufacturing process.
In a process of the diffusion welding, when the laminated structure body is gripped by the pair of jig members, a gas (e.g., air) is shut up in cavities such as the manifold chambers and pressure chambers that are formed in the laminated structure body, since the cavities are tightly closed by the pair of jig members. If the laminated structure body is heated at the high temperature to carry out the diffusion welding and is then cooled, the gas shut up in the cavities is caused to expand and contract, leading to considerable fluctuation of a pressure of the gas in the cavities and accordingly causing a risk of partial deformation of the laminated structure body. Further, increase of the pressure of the gas in the cavities would cause failure of fixation of the metal plates in vicinity of the cavities, thereby causing a risk of leakage of an ink from the ink channels.